Revert to default scale when seed changed?
Your approach doesn't explicitly set the scale of all objects, some of which might have been scaled to zero at some point, so their scale never reset.

To fix that, generate a list that define the state of each object, then use that list to control the scale of objects in whichever way you want. It is clear to me that you want to control how many objects gets scaled to zero, so to implement that, we are going to generate a list that has a certain number of zeros, with ones for the rest of the list, such list can be generated using the Fill List node. To make sure it is randomized, we can shuffle it or shuffle the object list itself as follows: